The present invention relates to examination methods and in particular to devices for preparation of histological specimens for microscopic examination.
In order to prepare histological specimens for microscopic examination the specimens taken for examination are successively subjected to the steps of fixation, e.g. in an aqueous formaldehyde solution, dehydration, clearing, and infiltration with paraffin or another suitable wax. The step of dehydration includes treatment of the fixed specimens with an alcohol reagent of gradually increasing concentration. During the clearing stage the specimens are once or several times treated with a clearing agent, e.g. xylene. Infiltration with paraffin (or another wax) is carried out by likewise repeatedly immersing the dehydrated and cleared specimens in melted paraffin or other wax. Only after the above processing steps have been completed a histological specimen is ready for microtoming.
Processing and infiltration of histological specimens may be carried out and often are carried out manually. In this case a lab assistant immerses cassettes with histological specimens in a vessel, adds the required fluids, agitates the vessel, pours away the fluids, places the vessel with the cassettes or the cassettes in a heating or cooling device etc. Manual processing and infiltration of histological specimens is quite labor-intensive and requires qualified staff, while the results obtained are not always reproducible. Laboratories that are specialized in histological examination use automated processing and infiltration devices.
The device for processing and infiltration of histological specimens according EP 0269316 is a multi-chamber apparatus comprising 12 chambers, which are arranged to form a circle, and a means for lifting the container with the specimen holding cassettes and moving them from one chamber to the next. The means is placed on an axis which is connected to a drive located inside the circle of chambers. The circle of chambers has a common cover with an openable opening over each chamber. The means for moving the container is encased. The device is processor-controlled. Cassettes with specimens are inserted in the container which is hung from the rocker of the means for moving the container inside the case. In the mode entered said means immerses the container with the specimens in each of the chambers containing the required reagents, takes the container out, and moves it to the next chamber.
The device according to EP 0269316 provides automated processing and infiltration of histological specimens, but it is not hermetically sealed what may entail pollution of the air in the laboratory with harmful substances, e.g. xylene; it is also not possible to use vacuum at each processing stage.
The device for processing and infiltration of histological specimens according to EP 0077477 includes a chamber for processing the specimens, several tanks for reagents, which are connected to the chamber by a separate valve system, a vacuum pump and a switchable valve system which is connected to the chamber and controls the direction of the reagent""s flow. The valve system and the vacuum pump provide a closed cycle for the exchange of the reagents and gases in the system of the chamber and the tanks for the reagents. The device according to EP 0077477 is automated and is controlled by a processor. The program for processing and infiltration of the histological specimens is executed without intervention of an operator. It is also not necessary to take any precaution when using harmful or toxic fluids.
In the devices as mentioned above processing time for a specimen with each consecutive fluid only depends on the diffusion speed of the displaced fluid from the surface of the specimen. In order to intensify the process stirring devices may be used, which, however, do not provide effective exchange of fluids in the arrangement of the cassettes with the specimens.
The device for processing and infiltration of histological specimens according to German Patent No. 3042578 comprises an incubation chamber, in which in pipe cylinders fluid-permeable containers for histological specimens are vertically arranged one on top of the other. A powerful vertical axial pump in the form of a worm or a plunger is located in the middle of the chamber, it forces the processing and infiltration fluids to circulate in the chamber and to flow downward through the pipe cylinders and the containers with the specimens which are located in these cylinders. The continues flow of the fluids around the specimens as described in German Patent No. 3042578 certainly aids in the intensification of the process, but the suggested arrangement of containers provides only poor efficiency.
The device for processing and infiltration of histological specimens according U.S. Pat. No. 4,576,798 also provides processing and infiltration of specimens in a fluid flow. The device comprises an encased vertical rotation axis located in the circular (in plan) case centrally, and a circular rotor which is located on the axis perpendicular to it; several channels that are tilted by 2-5xc2x0 from center to periphery are formed on the upper surface of the rotor. Depressions are formed near the peripheral end of each channel, in which are disposed perforated containers for the specimens. A hole from which the channels branch off is formed in the center of the rotor. The channels have their continuation from the depressions for the specimens to the edge of the rotor. The device comprises a means for rotating the axis and the rotor, tanks for processing and infiltration fluids and branch pipes for feeding fluids to the case and removing them from the case. The said fluid feeding branch pipe is directed to the hole.
The dehydrating and clearing fluids and the melted paraffin are supplied from the corresponding tanks to the central hole through the branch pipe; the rotation of the rotor forces the fluids to flow in the channels and around the histological specimens, which are located in the depressions at the periphery of the rotor. Processing in the fluid flow provides improved process efficiency. Prior to changing the processing fluid the motor may be switched to a higher rotation rate for removing the previous fluid by centrifuging; this speeds up processing and makes it more efficient. As metal consumption for each specimen to be treated is quite high and as it is possible to insert only few specimens in the device simultaneously, the device according to U.S. Pat. No. 4,576,796 is not very efficient.
Applied for is a device for processing and infiltration of histological specimens with high productivity as well as high effectiveness in processing and infiltration.
The device for processing and infiltration of histological specimens according to the present invention comprises a rotating means, which is located in a case and consists of a rotation axis with attached containers for cassettes with histological specimens, a means for rotating said rotation axis at variable speed, tanks for processing and infiltration fluids, which are located outside said case, and branch pipes for feeding said fluids to said case and removing them from said case. Additionally said rotation axis of said rotating means is positioned in said case horizontally, said containers for the cassettes with histological specimens are designed as ring sectors which are arranged to form a ring, whereby the inner diameter of said ring is 2-4 times the width of a cassette for histological specimens, and said ring of containers is mounted on the horizontal axis in the vertical plane.